2, 3, 7, 8-Tetrachlorodibenzo-p-dioxin (TCDD) is a persistent, lipophilic environmental contaminant that exerts toxicity through binding the aryl hydrocarbon receptor (AhR). The overall goal of this research is to understand how exposure to TCDD and other AhR agonists disrupts development of the forebrain and cerebral vasculature and, ultimately, how AhR agonist exposure may contribute to neurodevelopmental disorders and cognitive impairment. My preliminary data suggest that early embryonic exposure to TCDD severely disrupts the development of the forebrain and associated cerebral vasculature in zebrafish. The genetic and molecular tools available in zebrafish make it an excellent model for studying neurovascular development and toxicity. However, relatively few studies have used the zebrafish model to examine how TCDD-induced activation of Ahr2 impacts brain and cerebral vascular development. In Aim 1, using confocal microscopy, fluorescent- immunohistochemistry (F-IHC) and Olympus software, the candidate will create 3D reconstructions of TCDD-exposed and control brains for a detailed analysis and quantification of forebrain phenotypes. TCDD-induced changes in the cerebral vasculature will be quantified using AngioTool software. In addition, the candidate will use exciting new imaging technology to examine cerebral vascular development in vivo, which will provide unique insight into how TCDD-induced phenotypes emerge. In Aim 2, the candidate will manipulate Ahr2 activity in a cell-type specific manner to determine if activation of Ahr2 in either vascular endothelial cells or differentiated neurons is sufficient to produce the observed forebrain and cerebral vascular phenotypes. Downregulation of the transcription factor, sox9b, has emerged as a common mechanism mediating TCDD-induced toxicity in the heart, jaw and fin. Preliminary data indicates sox9b expression in the forebrain is downregulated following TCDD exposure and that loss of sox9b results in forebrain and cerebral vascular phenotypes that resemble TCDD-induced forebrain and cerebral vascular phenotypes. In Aim 3, the candidate will determine if sox9b is also a TCDD target in the developing brain and elucidate sox9b function(s) in the development of the forebrain and cerebral vasculature. Importantly, the proposed research will help us understand how AhR activation disrupts neurovascular development and when neurovascular phenotypes emerge during development. This information is essential for understanding potential risks associated with human AhR agonist exposure. The brain is a metabolically intense organ that is highly dependent on proper and continuous cerebral vascularization for normal function. Consequently, this work is relevant not only to embryonic development, but also later life stages. As a K award recipient, the candidate will follow a training plan that outlines very specific research and career development milestones to be reached over the course of the award. To augment my research background in Neuroscience, Developmental Genetics, and Cardiovascular Toxicology, my research aims are coupled with didactic coursework and hands-on training in Neurovascular Biology, Molecular Biology and Neurotoxicology. The activities outlined in this training application will provide me with training in areas needed for a successfu research career including grantsmanship, project design, and laboratory management. A committee composed of an outstanding team of scientists has been assembled is committed to the candidate and her success and are willing to play an active role in facilitating my growth as a scientist. The University of Wisconsin is a top-tier research institute with numerous NIH-sponsored training programs, core facilities, and outstanding researchers, which makes it an ideal training environment for me to develop as an independent scientist. Ultimately, the training in my research and career development plan, my interactions with my mentors, committee members and consultants, and my outstanding training environment will provide an excellent foundation for a successful academic career at a research intensive academic institution.